Taking the pulse of Nate Silver's numbers

(CBS News) After crunching the numbers, our CBS News polling unit currently shows President Obama with the narrowest of leads over challenger Mitt Romney. Subject to change over the next three days, of course. The promise and peril of high-tech vote prediction was first demonstrated live on our air back in 1952 . . . as Martha Teichner reminds us now in our "Sunday Morning" Cover Story:

It wasn't just the first coast-to-coast broadcast of a presidential election, and Walter Cronkite's first time anchoring on election night; 1952 marked the first time a computer was used to project the winner.

Laughable now, groundbreaking then.

"Univac, can you tell us a prediction now? I think that Univac is probably an honest machine . . . "

But Univac did have something to say. With not even 3 1/2 million votes counted, "he" predicted 100 to 1 odds of an Eisenhower victory, in a landslide so huge it seemed impossible, given what was then thought to be a close race. The results were withheld for several hours, fearing humiliation. But Univac was right.

The war between the stat heads and the pundits had begun.

Fast-forward 60 years, to 2012, and we have New York Times blogger Nate Silver's prediction of an Obama win on Tuesday, no matter what the popular vote:

"We have him as a 75 percent favorite roughly, almost an 80 percent favorite, in fact, to win in the Electoral College, less than that in the popular vote," said Silver. "Politics is full of people who are trained to manipulate the way that we view information, so when they see information that they don't like - based on what our computer program that we designed four years ago says every day - they're going to become very, very upset.

"Nate Silver says this is a 73.6 percent chance that the president is going to win? Nobody in that campaign thinks they have a 73 percent chance, they think they have a 50.1 percent chance of winning," former Republican Congressman Joe Scarborough said last week on MSNBC's "Morning Joe." "And you talk to the Romney people, it's the same thing."

"And anybody that thinks that this race is anything but a toss-up right now, they're jokes."

Silver argues that the race is tight, but not a toss-up. He calls his blog 538, because that's the total number of Electoral College votes; a presidential candidate has to get at least 270 Electoral Votes to win. No other number really matters, and Silver's computer model says President Obama is ahead in the states capable of delivering that magic 270 - namely, Ohio, Wisconsin, Nevada and Iowa.

So how does this model work?

"Every poll that people read about goes into the model and feeds the projection in some way," Silver told Teichner.

There might be 30 or 40 of them a day, in this year's poll-happy universe. Silver's model averages all those polls, then factors in how well they've performed in past elections, and comes up with probabilities, like gambling odds.

"So in Florida, for example, we had Romney with a 60 percent chance of winning. That's how often, when you have a one-point lead in the average of polls, you've wound up winning in the past. In Ohio, we have Obama with about a 75 percent chance of winning, because he has a larger lead, and so it's more likely to be enduring on Election Day itself."